The Fat Man, a popular radio show during the 1940s and early 1950s, was a detective drama created by Dashiell Hammett, author of The Thin Man. It starred J. Scott Smart in the title role, as an overweight detective who started out anonymous but rapidly acquired the name 'Brad Runyon'.
Not who you're looking for? Others named The Fat Man: song by Fats Domino · 1951 film by William Castle